Why is a second cin.ignore() necessary?

Question

I\'ve noticed that whenever I write a program that uses std::cin that if I want the user to press Enter to end the program, I have to write std::cin.ignor

Answer 1

Discl: I'm simplifying what really happens.

The first serves to purge what the extraction operator (>>) hasn't consumed. The second waits for another \n.

It is exactly the same when we do a std::getline after an extraction: a the_stream::ignore(std::numeric_limits::max(), '\n'); is required before the call to std::getline()